Direction of Arrival Estimation of Acoustic-Signals From Acoustic Source Using Sub-Array Selection

ABSTRACT

A system that handles direction of arrival (DOA) estimation for acoustic signals using sub-array selection, identifies a plurality of microphone sub-arrays from the plurality of microphones in the microphone-array, selects a set of microphone sub-arrays from the plurality of microphone sub-arrays, and computes a relative time-delay for arrival of the acoustic signals between each pair of microphones of the selected set of microphone sub-arrays. The selection is based on a maximum distance between each pair of microphones of the identified plurality of microphone sub-arrays of the microphone-array. A first microphone sub-array is determined from the selected set of microphone sub-arrays and the DOA of the acoustic signals is estimated with reference to the determined first microphone sub-array. The estimation of the direction of arrival of the acoustic signals is based on the computed relative time-delay for the determined first microphone sub-array of the microphone-array.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

None.

FIELD OF TECHNOLOGY

Certain embodiments of the disclosure relate to direction of arrivalestimation technologies. More specifically, certain embodiments of thedisclosure relate to estimation of direction of arrival of signals froman acoustic source using sub-array selection.

BACKGROUND

The direction of arrival (DOA) estimation of acoustic signals is anactive area of research for different applications, such as virtualassistants, camera pointing systems (in video conferencing),teleconferencing, improved human-machine interactions, voice activateddevices, home automation, and the like. An accurate DOA estimationfurther contributes to enhancement in automatic speech recognition ofdistant or differentially positioned users, spatial audio coding, andseparation of different acoustic sources in a given acoustic data.

Many DOA estimation techniques have been proposed and have evolved fromthe origin of antenna theory to the present-day technologies. Amongthese techniques, time-delay-of-arrival (TDOA) based DOA estimation,Multiple Signal Classification (MUSIC), Steered Response Power-PhaseTransform (SRP-PHAT) and Generalized Cross Correlation (GCC), andestimation of signal parameters based on rotational invariance (ESPRIT)techniques have received considerable attention as they providereasonable DOA accuracy in certain application scenarios. Suchaforementioned techniques may differ based on different levels ofimplementation complexity. For example, MUSIC method may requiredifferent a priori knowledge of acoustic sources to operate, which maybe unavailable or difficult to model in complex acoustic scenarios.

MUSIC is further known to operate in moderate and high signal-to-noiseratio (SNR) conditions; however, it barely works when the SNR is low.Further, there is an imbalance between computational complexity andaccuracy with applications or systems that employ the MUSIC techniquefor DOA estimation. The SRP-PHAT technique is computationally veryintensive as it considers all the correlations of microphone pairsfollowed by a search process in the DOA estimation. Additionally, forSRP-PHAT technique, the direction of the reflections of the acousticsignals from a speaker may exhibit greatest steered power, which mayresult in inaccurate DOA estimation. Similarly, for the GCC method, themaximum cross-correlation could occur at a spurious delay if the systemis used in reverberant environments. Such spurious delay may be createdby the ensuing reflections that result in inaccurate DOA estimation.Therefore, the aforementioned techniques poses a challenge to provide acomputationally less intensive solution for DOA estimation of acousticsignals in lesser amount of time and thus, ensuring a high throughput ofDOA estimation data.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present disclosureas set forth in the remainder of the present application with referenceto the drawings.

BRIEF SUMMARY OF THE DISCLOSURE

Systems and/or methods are provided for estimation of direction ofarrival of signals from an acoustic source using sub-array selection,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentdisclosure, as well as details of an illustrated embodiment thereof,will be more fully understood from the following description anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram that illustrates an exemplary environment forestimation of direction of arrival of signals from an acoustic sourceusing sub-array selection, in accordance with an exemplary embodiment ofthe disclosure.

FIG. 2 is a block diagram that illustrates an exemplary signalprocessing apparatus estimation of direction of arrival of signals froman acoustic source using sub-array selection, in accordance with anexemplary embodiment of the disclosure.

FIGS. 3A and 3B are exemplary scenarios that illustrate a configurationof a microphone-array for estimation of direction of arrival of signalsfrom an acoustic source using sub-array selection by the signalprocessing apparatus of FIG. 2, in accordance with an embodiment of thedisclosure.

FIG. 4 is a flowchart that illustrates exemplary operations forestimation of direction of arrival of signals from an acoustic sourceusing sub-array selection, in accordance with various exemplaryembodiments of the disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Certain embodiments of the disclosure may be found in a system andmethod for estimation of direction of arrival of acoustic signals usingsub-array selection. The present disclosure may provide severaladvantages over the traditional direction of arrival (DOA) estimationsolutions. In contrast to conventional techniques, such as SRP-PHAT orGCC, where DOA is estimated using time-delays of all the possible pairsof microphones, the disclosed system and method provides a robust andoptimal solution, where DOA may be estimated using the time-delays ofonly selected sub-arrays of a microphone-array. The sub-array selection(i.e., decomposition) feature facilitates in filtering out the undesiredpairs from the possible pairs of microphones with effectivethresholding. This reduces the computational complexity and enables afaster estimation of DOA.

Various embodiments of the disclosure provide a system that may includea microphone-array comprising a plurality of microphones. The system mayfurther include a signal processing apparatus communicatively coupled tothe microphone-array. The signal processing apparatus may comprise aplurality of circuits (hereinafter, referred to as “circuits”). Thecircuits may be configured to identify a plurality of microphonesub-arrays from the plurality of microphones in the microphone-array.Each microphone sub-array of the identified plurality of microphonesub-arrays may comprise a pair of microphones spaced apart by a specificdistance. The circuits may be further configured to select a set ofmicrophone sub-arrays from the identified plurality of microphonesub-arrays of the microphone-array. The selection may be based on amaximum distance between each pair of microphones of the plurality ofmicrophone sub-arrays of the microphone-array. A relative time-delay maybe further computed for an arrival of the acoustic signals between eachpair of microphones of the selected set of microphone sub-arrays. Therelative time-delay may correspond to an estimated time-delay for thearrival of acoustic signals between each pair of microphones of theselected set of microphone sub-arrays. Further, the circuits may beconfigured to determine a first microphone sub-array from the selectedset of microphone sub-arrays. The first microphone sub-array may bedetermined based on a maximum time-delay from the computed relativetime-delay for each of the selected set of microphone sub-arrays. Thefirst microphone sub-array may be a desired microphone sub-arraydetermined from the identified plurality of microphone sub-arrays in themicrophone-array. The circuits may further estimate a direction ofarrival (DOA) of the acoustic signals with reference to the determinedfirst microphone sub-array, based on the computed relative time-delayfor arrival of the acoustic signals at the determined first microphonesub-array.

In accordance with an embodiment, the direction of arrival of theacoustic signals with reference to the determined first microphonesub-array may be estimated based on one or more parameters. The one ormore parameters may comprise a sampling frequency of the acousticsignals, a speed of the acoustic signals, the computed relativetime-delay for the determined first microphone sub-array, and a radiusassociated with a planar arrangement of the microphones in themicrophone-array. Further, the direction of arrival of the acousticsignals may be estimated in one of a frequency domain and a time domainand a direction that corresponds to a location of the signal source issame as the direction of arrival of the acoustic signals.

In accordance with an embodiment, the direction of arrival of theacoustic signals with reference to the determined first microphonesub-array may be estimated based on a digital filter that processes theacoustic signals received at a first microphone and a second microphoneof the determined first microphone sub-array. The digital filter for theestimation of the direction of arrival of the acoustic signals may beone of an infinite impulse response (IIR) filter or finite impulseresponse (FIR) filter. The digital filter may process the acousticsignals based on one of a cross-correlation, a Fast Fourier Transform(FFT), a Discrete Fourier Transform (DFT) of the acoustic signalsreceived at the first microphone and the second microphone of thedetermined first microphone sub-array.

The plurality of circuits may be further configured to determine thespecific distance between the pair of microphones of the plurality ofmicrophone sub-arrays of the microphone-array. The plurality ofmicrophones may be arranged in the microphone-array in a regular convexpolygon arrangement such that each microphone in the microphone-arraymay be arranged at vertices of the regular convex polygon. The selectionof the set of microphone sub-arrays from the microphone-array may bebased on a planar arrangement of the set of microphone sub-arrays thatbisect each other in the microphone-array.

The first microphone sub-array may be determined from the selected setof microphone sub-arrays based on a maximum of the computed relativetime-delay among the selected set of microphone sub-arrays. The relativetime-delay for the selected set of microphone sub-arrays may be computedbased on a cross-correlation of the acoustic signals received at twodifferent microphones of the selected set of microphone sub-arrays. Thecomputation of the relative time-delay may be done for each selectedmicrophone sub-array instead of computation of the relative time-delayfor each microphone sub-array in the microphone-array.

The disclosed system and method proactively mitigates a possibility thatthe time-delay of determined first microphone sub-array (i.e., thedesired microphone sub-array) may be dominated by time-delays of othermicrophone sub-arrays, which may result in inaccurate estimation of DOA.The disclosed method proactively mitigates such possibility ofinaccurate estimation with efficient thresholding of time-delays. Theprecise DOA estimation may further facilitate dependent systems toprecisely deliver solutions for different applications, in a robust andadaptive manner.

FIG. 1 is a block diagram that illustrates an exemplary environment forestimation of direction of arrival of signals from an acoustic sourceusing sub-array selection, in accordance with an exemplary embodiment ofthe disclosure. In FIG. 1, there is shown a communication environment100 that comprises a signal processing apparatus 102, a signal source104, a microphone-array 106, one or more communication devices 108, adata server 110, and a communication network 112.

In accordance with an embodiment, as illustrated in FIG. 1, themicrophone-array 106, the one or more communication devices 108, and thedata server 110 may be communicatively coupled to the signal processingapparatus 102, via the communication network 112, to form a direction ofarrival estimation system. However, the disclosure may not be solimited, and in accordance with another embodiment, the microphone-array106 and the signal processing apparatus 102 may be integrated as asingle device, without deviation from the scope of the disclosure.

The communication environment 100 may correspond to a closed environmentor an open environment. Examples of the closed environment may include,but are not limited to, interiors of offices, physical stores, vehicles,indoor stadiums, airplane, or halls. Examples of the open environmentmay include, but are not limited to, an outdoor area, road, outdoorstadiums, swimming pools, rocky terrains, or ship decks. In accordancewith an embodiment, the communication environment 100 may furthercomprise at least one of a reverb source, a babble noise source, a whitenoise source, a Gaussian noise source, and a diffused noise field (notshown). Such sources may be detected and factored during execution ofoperations for estimation of a direction of arrival of acoustic signalsfrom the signal source 104.

The signal processing apparatus 102 may comprise suitable logic,circuitry, and interfaces that may be configured to process acousticsignals received at a set of microphone sub-arrays of themicrophone-array 106. The signal processing apparatus 102 may be furtherconfigured to estimate a direction of arrival (hereinafter, “DOA”) ofthe acoustic signals from the signal source 104, present in thecommunication environment 100. Examples of the implementation of thesignal processing apparatus 102 may include, but are not limited to, aDOA estimation device, an audio/video conferencing system, an automaticcamera steering system, a human-machine interface, a speech processingsystem, a speaker system, a gaming device, an audio surveillanceapparatus, and other electronic devices that process the acousticsignals.

The signal source 104 may comprise suitable logic, circuitry, andinterfaces that may generate acoustic signals. The acoustic signals maybe generated for one or more users present in the communicationenvironment 100. Alternatively, the acoustic signals may be generated astest signals for the estimation of DOA of the acoustic signals. Inaccordance with an embodiment, the signal source 104 may be aspeaker-device integrated or peripherally coupled with one of atelevision, a mobile phone, a music-system, or a sound/speech outputsystem. In accordance with an exemplary embodiment, the signal source104 may be different sound emitting sources, for example, ahuman-speaker or a group of human-speakers present in defined limits ofthe communication environment 100. In accordance with an embodiment, thesignal source 104 may be implemented as a network-enabled speaker thatretrieves media from the data server 110, via the communication network112. In some embodiments, the playback of the media may generate theacoustic signals.

The microphone-array 106 may comprise suitable logic, circuitry, andinterfaces that may be configured to receive (or capture) the acousticsignals from the signal source 104. Thereafter, the microphone-array 106may be configured to transmit the acoustic signals to the signalprocessing apparatus 102, for the estimation of the DOA of the acousticsignals. The microphone-array 106 may comprise a plurality ofmicrophones, from which a plurality of microphone sub-arrays may beidentified. Each microphone sub-array of the identified plurality ofmicrophone sub-arrays may comprise a pair of microphones, which may bespaced apart by a specific distance in the microphone-array 106. Theplurality of microphones may be arranged in the microphone-array 106 ina regular convex polygon arrangement, such as a regular hexagon. Thearrangement of the plurality of microphone in the microphone-array 106is shown and described, for example, in FIGS. 3A and 3B. Each microphonein the microphone-array 106 may be arranged at vertices of the regularconvex polygon arrangement. In some embodiments, the microphone-array106 may be implemented as a separate device that may be communicativelycoupled to the signal processing apparatus 102. In some embodiments, themicrophone-array 106 and the signal processing apparatus 102 may beimplemented within an integrated apparatus.

The one or more communication devices 108 may comprise suitable logic,circuitry, and interfaces that may be configured to receive theestimated DOA of the acoustic signals from the signal processingapparatus 102. Each communication device of the one or morecommunication devices 108 may be communicatively coupled with the signalprocessing apparatus 102, via the communication network 112. Eachcommunication device may be a networked or a stand-alone computationdevice for a specific application or systems associated with theestimation of the DOA of the acoustic signals emanated from signalsource 104. Example of the specific application or systems may include,but are not limited to, virtual assistants, camera pointing systems,video conferencing, teleconferencing, human-machine interfaces,voice-activated services, or home-automation control. Other examples ofthe one or more communication devices 108 may include, but are notlimited to, speakers, smart-speakers, workstations, servers, laptops,desktop computers, mobile devices, non-mobile devices, input/output(I/O) devices, and virtual machines.

The data server 110 may comprise suitable logic, circuitry, andinterfaces that may be configured to receive, manage, store, andcommunicate data, such as audio data or speech data, with at least oneof the signal processing apparatus 102 and the one or more communicationdevices 108, via the communication network 112. In a certainimplementation, the acoustic signals (as sound files) may be digitallystored at (or streamed by) the data server 110. Such an implementationof the data server 110 may be found in applications, such as videoconferencing, remote call conferencing, or other DOA-specific tasks,where a primary source of the acoustic signals may be present remotelywith reference to the signal source 104.

The communication network 112 may comprise suitable logic, circuitry,and interfaces that may be configured to provide a plurality of networkports and a plurality of communication channels for transmission andreception of data, such as instructions or storable versions of theacoustic signals. The communication network 112 may be a wired orwireless communication channel or network. Examples of the communicationnetwork 112 may include, but are not limited to, a Wireless Fidelity(Wi-Fi) network, a Local Area Network (LAN), a wireless personal areanetwork (WPAN), a Wireless Local Area Network (WLAN), a wireless widearea network (WWAN), a cloud network, a Long Term Evolution (LTE)network, a plain old telephone service (POTS), a Metropolitan AreaNetwork (MAN), and/or the Internet. Various devices in the exemplarycommunication environment may be configured to connect to thecommunication network 112, in accordance with various wired and wirelesscommunication protocols. Examples of such wired and wirelesscommunication protocols may include, but are not limited to,Transmission Control Protocol and Internet Protocol (TCP/IP), UserDatagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), FileTransfer Protocol (FTP), ZigBee, EDGE, infrared (IR), IEEE 802.11,802.16, Long Term Evolution (LTE), Light Fidelity (Li-Fi), and/or othercellular communication protocols or Bluetooth (BT) communicationprotocols, including variants thereof.

In operation, the signal source 104 may emit acoustic signals in thecommunication environment 100. The generated acoustic signals maycomprise at least one of a speech signal, an audio beacon, and an audiosignal different from the speech signal. The audio beacon may beultrasonic audio beacons or audible audio beacon. Such acoustic signalsmay be transmitted such that at least one lobe of the acoustic signalsmay point in a specific look direction or region of the communicationenvironment 100. The acoustic signals may be spread as omnidirectionalsignals in the communication environment 100 with a uniform ornon-uniform distribution of signal energy. In certain situations, a partor majority of the acoustic signals may be directed towards a regioncomprising the microphone-array 106.

The signal processing apparatus 102 may be communicably coupled witheach microphone in the microphone-array 106, via one of electricalbuses, wireless communication channels, or the communication network112. In accordance with an embodiment, the signal processing apparatus102 may be activated based on monitoring of activities or certainapplication-specific operations within the communication environment100. In some embodiments, the signal processing apparatus 102 may beactivated based on a trigger signal. Such trigger signal may be receivedbased on detection of acoustic signals in the communication environment100, a speech-input from a human-speaker, or receipt of data from themicrophone-array 106.

Initially, the signal processing apparatus 102 may be configured toidentify a plurality of microphone sub-arrays from the plurality ofmicrophones in the microphone-array 106. Each identified microphonesub-array of the plurality of microphone sub-arrays may comprise a pairof microphones spaced apart by a specific distance, for example, aspecific distance equal to a length of a diagonal of a hexagonal planararrangement of microphones in the microphone-array 106. Alternativelystated, the identified plurality of microphone sub-arrays may correspondto the possible number of microphone pairs, where the two microphones ofa microphone pair are separated by a maximum distance in themicrophone-array 106.

The signal processing apparatus 102 may be further configured to selecta set of microphone sub-arrays from the identified plurality ofmicrophone sub-arrays of the microphone-array 106. The selection of theset of microphone sub-arrays may be based on a maximum distance betweeneach pair of microphones of the identified plurality of microphonesub-arrays of the microphone-array 106. Such selection of the set ofmicrophone sub-arrays may be referred to as sub-array decomposition ofthe microphone-array 106. The selection of the set of microphonesub-arrays may be done further based on a planar arrangement of theplurality of microphone sub-arrays that bisect each other in themicrophone-array 106.

In accordance with an embodiment, the plurality of microphones may bearranged in the microphone-array 106 in a regular convex polygonarrangement with even number of microphones, where each microphone inthe microphone-array 106 may be arranged at vertices of the regularconvex polygon. The selection of the set of microphone sub-arrays in themicrophone-array 106 may be done further based on a specific alignmentof different pairs of microphones of the set of microphone sub-arrays.For example, each selected microphone sub-array may include a pair ofmicrophones in which one microphone may be aligned diagonally oppositeto other microphone.

In some embodiments, the signal processing apparatus 102 may selectivelyactivate each microphone in the selected set of microphone sub-arrays toreceive the acoustic signals from the signal source 104. The signalprocessing apparatus 102 may further compute a relative time-delay foreach microphone sub-array of the selected set of microphone sub-arrays.The relative time-delay may correspond to an estimated time-delay forthe arrival of acoustic signals between each pair of microphones of theselected set of microphone sub-arrays. In some embodiments, for eachselected microphone sub-array, the relative time-delay may be computedfrom a cross-correlation of the acoustic signals at each microphone inthe pair of microphones of the selected set of microphone sub-arrays.The computed relative time-delay for each selected microphone sub-arraymay be compared only with other selected microphone sub-arrays insteadof all microphones in the microphone-array 106. The comparison mayfurther be factored on the basis of a maximum value of time-delay, forexample a maximum time-delay of “3.5 milliseconds” for a pair (1,4) ofmicrophones, from a set of time-delay of “1.8 milliseconds”, “2.5milliseconds”, and “3.5 milliseconds”. A primary purpose ofdetermination of the microphone sub-array with the maximum relativetime-delay is to identify a desired microphone pair that is alignedalong an axis with a minimum angular separation (or nearest to) from thesignal source 104 (See FIGS. 3A and 3B for example).

Based on the comparison, the signal processing apparatus 102 may beconfigured to determine a first microphone sub-array from the selectedset of microphone sub-arrays. The determined first microphone sub-arraymay be a desired microphone sub-array from the identified plurality ofmicrophone sub-arrays in the microphone-array 106. The determined firstmicrophone sub-array may exhibit a maximum relative time-delay ascompared to other microphone sub-arrays in the microphone sub-array.With computation of the relative time-delay for each selected microphonesub-array, a region may be determined that may be utilized to estimatethe DOA of the acoustic signals with respect to the desired microphonesub-array. The region may be defined by an angular distance withreference to a radial axis associated with the microphone-array 106.

To further determine an exact DOA of the acoustic signals, thedetermined first microphone sub-array may be selected as the desiredradial axis for determination of a relative angular separation of thedetermined first microphone sub-array from the signal source 104.Thereafter, the signal processing apparatus 102 may estimate the DOA ofthe acoustic signals based on the computed relative time-delay for thedesired microphone sub-array. Alternatively stated, the signalprocessing apparatus 102 may utilize the relative time-delay computedpreviously for the desired (or the first) microphone sub-array toestimate the DOA of the acoustic signals. The DOA of the acousticsignals may be same as an angular separation of the signal source 104from the determined first microphone sub-array.

FIG. 2 is a block diagram that illustrates an exemplary signalprocessing apparatus for estimation of DOA of acoustic signals from anacoustic source using sub-array selection, in accordance with anexemplary embodiment of the disclosure. FIG. 2 is described inconjunction with elements from FIG. 1. In FIG. 2, there is shown a blockdiagram of the signal processing apparatus 102 that may include aplurality of circuits 200, such as a network interface 202, anInput/output (I/O) unit 204, a processor 206, an array selector 210, anda DOA estimator 212. The signal processing apparatus 102 mayadditionally include a memory 208 communicably coupled to the I/O unit204, the processor 206, and the network interface 202.

The network interface 202 may comprise suitable logic, circuitry,interfaces that may be configured to communicate with other systems anddevices communicably coupled to the signal processing apparatus 102, viathe communication network 112. The network interface 202 may beimplemented by use of known technologies to support wired or wirelesscommunication of the signal processing apparatus 102 with thecommunication network 112. Components of the network interface 202 mayinclude, but are not limited to, an antenna, a radio frequency (RF)transceiver, one or more amplifiers, a tuner, one or more oscillators, adigital signal processor, a coder-decoder (CODEC) chipset, a subscriberidentity module (SIM) card, and/or a local buffer circuitry. The networkinterface 202 may be configured to communicate with the one or morecommunication devices 108, via the communication network 112, under thecontrol of the processor 206.

The I/O unit 204 may comprise suitable logic, circuitry, and interfacesthat may be configured to receive signal data from the microphone-array106 and information associated with the planar arrangement of eachmicrophone in the microphone-array 106. Additionally, the I/O unit 204may receive requests to fetch the signal data from the one or morecomponents, such as the data server 110 or the memory 208 of the signalprocessing apparatus 102. The I/O unit 204 may be configured to receiveone or more communication requests from external devices, such as thesmartphones, smart speakers, and televisions, a human speaker, or thedata server 110. The I/O unit 204 may include one or more physicalcommunication ports and one or more virtual network ports to facilitatereception and transmission of the communication requests and/or signaldata.

The processor 206 may comprise suitable logic, circuitry, and interfacesthat may be configured to process the acoustic signals from a set ofmicrophone sub-arrays of the microphone-array 106. The processor 206 maybe configured to perform various operations, such as computation oftransforms, responses, signal quantization, sampling, signalcompression, delay estimation, and/or phase estimation. The processor206 may be communicatively coupled with the network interface 202, theI/O unit 204, the memory 208, and other circuitries associated with thesignal processing apparatus 102. Examples of the processor 206 may be anApplication-Specific Integrated Circuit (ASIC) processor, a Digitalsignal processing (DSP)-based processor, a Complex Instruction SetComputing (CISC) processor, and/or other control circuits.

The memory 208 may comprise suitable logic, circuitry, and interfacesthat may be configured to store instructions and resources associatedwith execution of operations, for the estimation of the DOA of theacoustic signals that emanate from the signal source 104. Examples ofmemory 208 may include, but are not limited to, a static random accessmemory (SRAM), a dynamic random access memory (DRAM), a flash memory, anelectrically erasable programmable read-only memory (EEPROM), anerasable programmable read-only memory (EPROM), or a programmableread-only memory (PROM. Additionally, the memory 208 may be a magneticstorage drive (HDD) or a solid state drive (SSD) for a persistentstorage of the signal data. Alternatively, a set of centralized ordistributed network of peripheral memory devices may be interfaced andbridged with the signal processing apparatus 102, via the I/O unit 204.

The array selector 210 may comprise suitable logic, circuitry, andinterfaces that may be configured to select a set of microphonesub-arrays from the plurality of microphone sub-arrays in themicrophone-array 106. The set of microphone sub-arrays may be selectedin conjunction with operations executed by the processor 206 in thememory 208.

The DOA estimator 212 may comprise suitable logic, circuitry, andinterfaces that may be configured to estimate the DOA of the acousticsignals with reference to the microphone-array 106. The DOA of theacoustic signals may correspond to a relative angular separation betweena desired axis (of a specific microphone sub-array) of themicrophone-array 106 and the signal source 104. The DOA of the acousticsignals, associated with the signal source 104, may be determined inconjunction with operations executed by the processor 206 of the signalprocessing apparatus 102.

In operation, the processor 206 may be configured to receive controlsignals to initialize DOA estimation of the acoustic signals thatemanate from the signal source 104. The control signals may be receivedfrom circuits peripheral to the signal processing apparatus 102 orroutines executed within the signal processing apparatus 102. Forexample, a polling cycle in the processor 206 may be executed to checkfor relevant-activity in the communication environment 100. Example ofthe relevant-activity may include, but is not limited to, an arrival ofa signal source 104, an acoustic beacon from a media device, and aninput from a user, such as a voice-enabled input, a gesture-enabledinput, and a touch-enabled input.

The processor 206 may be configured to execute instructions or routinesalong with associated resources for different operations associated withthe DOA estimation of the acoustic signals with respect to the signalsource 104. The instructions or routines along with associated resourcesmay be stored in the memory 208. Accordingly, the processor 206 mayallocate process threads from a thread pool, to each operation for theDOA estimation of the acoustic signals, in near real time. Such anallocation may be serial or parallel such that the execution and resultsmay be generated in an optimal time-period.

In accordance with an embodiment, the signal processing apparatus 102may be communicably coupled to each microphone in the microphone-array106, via the communication network 112. In such an implementation, themicrophone-array 106 may communicate to the signal processing apparatus102 via the network interface 202 of the signal processing apparatus102. In accordance with an embodiment, the signal processing apparatus102 may be communicably coupled as a peripheral circuit, viacommunication buses or channels. In such an implementation, themicrophone-array 106 may communicate with the signal processingapparatus 102 via the I/O unit 204 of the signal processing apparatus102.

The array selector 210 may be configured to retrieve informationassociated with a planar arrangement of the microphone-array 106. Theinformation may be retrieved from one of storage, such as the memory208, in the signal processing apparatus 102 or a database on the dataserver 110. The information may comprise one or more attributes(hereinafter, “attributes”) associated with the microphone-array 106.The attributes may include, but are not limited to, a locationcoordinate of each microphone within the planar arrangement of themicrophone-array 106, a location coordinate associated with a center ofthe planar arrangement associated with the microphone-array 106, and aradius of the planar arrangement associated with the microphone-array106. The array selector 210 may further be configured to identify aplurality of microphone sub-arrays from the plurality of microphones inthe microphone-array 106. Each microphone sub-array of the identifiedplurality of microphone sub-arrays may comprise a pair of microphonesspaced apart by a specific distance. Such identification of theplurality of microphone sub-arrays may be based on possible pairs ofmicrophones evaluated from the retrieved attributes of themicrophone-array 106. Each sub-array in the microphone-array 106 maycomprise a pair of microphones, arranged at the vertices of the planararrangement, with even number of microphones.

For example, a microphone-array 106 may be arranged in a regular convexhexagon arrangement. The microphone-array 106 may comprise a total of“6” microphones, arranged at vertices of the regular convex hexagonarrangement. Based on the arrangement, a total of ⁶C₂ pairs ofmicrophones may be identified by the array selector 210, where ⁶C₂specifies a possible combination of pairs of microphones from a givenset of 6 microphones. Alternatively stated, the array selector 210 mayidentify 15 microphone sub-arrays in the microphone-array 106. Such 15sub-arrays may be specified as (1,2), (1,3), (1,4), (1.5), (1,6), (2,3),(2,4), (2,5), (2,6), (3,4), (3,5), (3,6), (4,5), (4,6), (5,6). Here,each number uniquely denotes a microphone in the microphone-array 106(as shown in FIG. 3A and FIG. 3B).

The array selector 210, in conjunction with the processor 206, may befurther configured to select a set of microphone sub-arrays from thepossible plurality of microphone sub-arrays, identified from themicrophone-array 106. The selection of the set of microphone sub-arraysmay be based on a maximum distance between each pair of microphones ofthe identified plurality of microphone sub-arrays of themicrophone-array 106. Such selection of the set of microphone sub-arraysmay be referred to as sub-array decomposition of the microphone-array106. The set of sub-arrays may be selected to identify a reference axisfor the DOA estimation of the acoustic signals that emanates from thesignal source 104. Additionally, it is advantageous to select the set ofsub-arrays from the plurality of microphone sub-arrays to minimize anumber of iterative computations for each identified plurality ofmicrophone sub-arrays (or possible pairs of microphones) of themicrophone-array 106. Therefore, the selection of the set of microphonesub-arrays advantageously reduces a redundancy in a number ofcalculations executed to optimally and swiftly estimate the DOA of theacoustic signals.

The selection of the set of microphone sub-arrays from themicrophone-array 106 may be further based on a planar arrangement of theplurality of microphone sub-arrays that bisect each other in themicrophone-array 106. Alternatively stated, only specific microphonesub-arrays may be selected that equally divide an area of the planararrangement of the microphone-array 106. For example, a microphonesub-array is selected when such sub-array is present along a diagonal ofthe regular hexagonal arrangement of the microphone-array 106 anddivides the hexagonal area into two equal halves. The selection of theset of microphone sub-arrays from the microphone-array 106 may befurther based on an alignment of different pairs of microphones of theset of microphone sub-arrays. Each selected microphone sub-array mayinclude a pair of microphones in which one microphone is aligneddiagonally opposite to other microphone. The array selector 210 may befurther configured to factor each of the aforementioned conditions, suchas, maximum separation, bisection, and alignment, to optimally selectthe set of microphone sub-arrays from the possible plurality ofmicrophone sub-arrays in the microphone-array 106.

After the selection, the DOA estimator 212 may be configured to computea relative time-delay for the arrival of the acoustic signals betweeneach pair of microphones of the selected set of microphone sub-arrays.In accordance with an embodiment, for each of the selected set ofmicrophone sub-arrays, the relative time-delay may be computed based ona cross-correlation of the acoustic signals received at two differentmicrophones of the selected set of microphone sub-arrays.

For example, the acoustic signals from the signal source 104 may berepresented as X(n). Accordingly, the acoustic signals received at afirst microphone and a second microphone of the selected set ofmicrophone sub-arrays may be represented as X₁(n) and X₂(n),respectively. X₁(n) and X₂(n) may be represented by equation (1) and (2)as follows:

X ₁(n)=aX(n+T ₁)  (1)

X ₂(n)=bX(n+T ₂)  (2)

Where “a” and “b” are signal amplitudes factors for the first microphoneand the second microphone of the selected set of microphone sub-arrays.“T₁” and “T₂” represents the time of arrival of the acoustic signals atthe first microphone and the second microphone, respectively. “T1” and“T2” is representative of phase shifts in the acoustic signals at thefirst microphone and the second microphone of the selected set ofmicrophone sub-arrays, respectively. The cross-correlation of the X₁(n)and X₂(n) may be computed in a frequency domain or time domain. Infrequency domain, the DOA estimator 212 may be configured to implement aFast-Fourier Transform (FFT) of the acoustic signals received at the twodifferent microphones of the selected set of microphone sub-arrays.

In continuation with the above example, the cross-correlation may berepresented as R₁₂(n) and given by equation (3) in time domain asfollows:

R ₁₂(n)=ΣX ₁(n)×X ₂(n−T)  (3)

From equation (3), the cross-correlation for the acoustic signals in thetime domain may be a discretized summation of a product of the acousticsignal at the first microphone and the time-delay acoustic signals atthe second microphone of the selected set of microphone sub-arrays. TheDOA estimator 212 may be further configured to estimate thecross-correlation of equation (3) in the frequency domain.

In some instances, the cross-correlation may be computed in time domain.Equations (3) may be given in frequency domain by equation (4) and (5)as:

R ₁₂(w)=FFT(X ₁(n))×Conjugate FFT(X ₂(n))  (4)

R ₁₂(w)=ke ^(jw(T) ¹ ^(−T) ² ⁾ |X(w)|²  (5)

where “k” is a constant, “w” is the frequency component of the acousticsignals received at the selected set of microphone sub-arrays of themicrophone-array 106, and |X(w)|² is the energy spectral-density of theacoustic signals X(n). From equation (4) and (5), the cross-correlationis a represented as a complex exponential form of the acoustic signalswhere (T₁-T₂) may provide the relative time-delay for one of theselected set of microphone sub-arrays. Similarly, the relativetime-delay for each of the selected set of microphone sub-arrays may becomputed and stored in the memory 208 of the signal processing apparatus102.

In accordance with another embodiment, the relative time-delay for eachof the selected set of microphone sub-arrays may be computed based on adefined digital signal processing technique in the time domain or thefrequency domain, for example, Phase Transform (PHAT), MaximumLikelihood Estimation (MLE), Adaptive Least Mean Square (LMS) Filter,Average Square Different Function (ASDF), and the like. The relativetime-delay may correspond to an estimated time-delay for the arrival ofacoustic signals between each pair of microphones of the selected set ofmicrophone sub-arrays. The relative time-delay may be computed for eachselected microphone sub-array instead of computation for each microphonesub-array in the microphone-array 106. Such reduction in number ofcomputations/measurements may advantageously reduce a complexity of theoperations and thereby facilitate faster estimation of the DOA of theacoustic signals. The computed relative time-delay may be stored in thememory 208 of the signal processing apparatus 102 and/or in a databaseof the computed relative time-delays.

The DOA estimator 212 may be further configured to determine a firstmicrophone sub-array from the selected set of microphone sub-arrays. Thedetermined first microphone sub-array may be a desired microphonesub-array from the identified plurality of microphone sub-arrays in themicrophone-array 106. The determined first microphone sub-array may havelowest angular separation with the signal source 104, with reference toa geometrical center of the planar arrangement of the microphone-array106. Accordingly, the determined first microphone sub-array may furtherexhibit a maximum relative time-delay. Such maximum delay may beexhibited because of a presence of the signal source 104 proximally to alongitudinal axis of the desired microphone sub-array. Therefore, theselection of the desired microphone sub-array may be based on a maximumtime-delay from the computed relative time-delay for each of theselected set of microphone sub-arrays.

In accordance with an embodiment, the determined first microphonesub-array may be determined from the selected set of microphonesub-arrays when an angular separation between the signal source 104 anda selected microphone sub-array is in a defined range. Such a conditionhas been quantitatively described in FIGS. 3A and 3B. For example, arelative time-delay for “5 microphone sub-arrays” may be “1milliseconds”, “2.92 milliseconds”, “2.88 milliseconds”, “3.14milliseconds”, and “2.8 milliseconds”. Therefore, the relativetime-delay of “3.14 milliseconds” may be identified as the maximumrelative time-delay and accordingly, the microphone sub-array with therelative time-delay of “3.14 milliseconds” may be set as the desiredmicrophone sub-array for the estimation of the DOA of the acousticsignals.

The DOA estimator 212 may be further configured to estimate the DOA ofthe acoustic signals with reference to the determined first microphonesub-array. In some embodiments, the estimation of the DOA of theacoustic signals may be done based on the computed relative time-delayfor arrival of the acoustic signals at the determined first microphonesub-array. Alternatively stated, the DOA may be estimated based on thecomputed relative time-delay for the desired microphone sub-array and arelationship of the computed relative time-delay with one or moreparameters (an example of the relationship is reflected in equation(6)). The one or more parameters may comprise a sampling frequency ofthe acoustic signals, a speed of acoustic signals, and a radiusassociated with a planar arrangement of the microphone-array 106.

For example, for “T_(D)” as the relative time-delay “T₁-T₂” for thedesired microphone sub-array (or the determined first microphonesub-array), “r” as radius of the planar arrangement, “f_(s)” as samplingfrequency, and “v_(s)” as speed of the acoustic signals, the DOA as “8”(in degrees) may be given by equation (6) and (7) as follows:

$\begin{matrix}{T_{D} = \frac{2{rf}_{s}\; \cos \; \theta}{v_{s}}} & (6) \\{{\theta\left( {{in}\mspace{14mu} {degree}} \right)} = {\cos^{- 1}\; \frac{T_{D}v_{s}}{2\; {rf}_{s}}}} & (7)\end{matrix}$

From equation (6) and (7), the DOA (θ) for the acoustic signals from thesignal source 104 may be a dependent on the relative time-delay (T_(D))for the desired microphone sub-array (or the determined first microphonesub-array), the speed of the acoustic signals (v_(s)), the radius (r) ofthe planar arrangement, and the sampling frequency (f_(s)). Ofaforementioned parameters, the DOA estimator 212 may parametricallyadjust the sampling frequency (f_(s)) and the radius (r) of themicrophone-array 106 to obtain optimum values that provide improvedresults for the direction of arrival of the acoustic signals. Further,the speed of the acoustic signals is usually a constant in a givenmedium, and therefore, the DOA (θ) is primarily dependent on therelative time-delay T_(D), and may be represented by equation (8) asfollows:

θ=cos⁻¹ k ₁ T _(D)=Function[T _(D)]  (8)

From equation (8), “k₁” is a constant value that comprises the radius(r), the sampling frequency (f_(s)), and the speed of the acousticsignals (v_(s)). Therefore, the value of θ is completely a function ofthe relative time-delay for the determined first microphone sub-array.

In other embodiments, the direction of arrival of the acoustic signalswith reference to the determined first microphone sub-array may beestimated based on a digital filter. Such digital filter may implement adefined signal processing technique and process the acoustic signalsreceived at a first microphone and a second microphone of the determinedfirst microphone sub-array, to estimate the DOA of the acoustic signals.The digital filter for the estimation of the DOA of the acoustic signalsmay be one of an infinite impulse response (IIR)-based filter or afinite impulse response (FIR)-based filter. Such IIR-based filter or theFIR-based filter may process the acoustic signals based on one of across-correlation, a Fast Fourier Transform (FFT), a Discrete FourierTransform (DFT) of the acoustic signals, and the like.

In some embodiments, the acoustic signals may be directed towards aregion different from the region comprising the microphone-array 106. Afraction of signal energy of the acoustic signals may suffer reflectionswith different types of reflecting surfaces in the communicationenvironment 100. Such reflections for the fraction of the signal energyassociated with the acoustic signals may cause a phase-shift of theacoustic signals and increase a noise-correlation in the acousticsignals. Therefore, different fractions of the acoustic signals mayreach the microphone-array 106 at different times. The signal processingapparatus 102 may factor such conditions and reflections of the acousticsignal while determining the DOA of the acoustic signal from the signalsource 104. In some embodiments, the arrangement of the microphone-array106 may be done such that the microphone-array 106 may be receptive andsensitive to the acoustic signals from every direction in thecommunication environment 100. Additionally, the position of themicrophone-array 106 in the communication environment 100 may beselected such that the microphone-array 106 may receive a maximum of thesignal energy associated with the acoustic signals. An extent of signalenergy of the acoustic signals that reaches the microphone-array 106 maybe further based on a distance between the signal source 104 and themicrophone-array 106, a plane of the signal source 104 and themicrophone-array 106, types of absorbing components in the communicationenvironment 100, and the signal energy of the acoustic signal.

FIGS. 3A and 3B are exemplary scenarios that illustrate a configurationof a microphone-array for estimation of direction of arrival of signalsfrom an acoustic source using sub-array selection by the signalprocessing apparatus of FIG. 2, in accordance with an embodiment of thedisclosure. FIGS. 3A and 3B are explained in conjunction with elementsfrom the FIGS. 1 and 2. With reference to FIG. 3A, there is shown themicrophone-array 106 communicatively coupled to the signal processingapparatus 102. As shown, the microphone-array 106 comprises a pluralityof microphones 302A to 302F. The plurality of microphones 302A to 302Fin the microphone-array 106 may be analyzed to identify a possibleplurality of microphone sub-arrays, of which a selected set ofmicrophone sub-arrays are shown in dotted lines in the FIG. 3A. Theselected set of microphone sub-arrays may comprise a first microphonesub-array 304A, a second microphone sub-array 304B, and a thirdmicrophone sub-array 304C.

The microphone-array 106 comprises six microphones, such as theplurality of microphones 302A to 302F, arranged at vertices of a regularhexagon. The plurality of microphone sub-arrays may be identified from asum of total number of diagonals and the number of sides of the planararrangement. The plurality of microphone sub-arrays (M(n)) may be givenby equation (9) as:

$\begin{matrix}{{M(n)} = {\frac{n\left( {n - 3} \right)}{2} + n}} & (9)\end{matrix}$

Where “n” represents the number of sides of the regular polygonarrangement. For example, using equation (9), the number of possiblemicrophone sub-arrays for a regular hexagon arrangement may be“6(6−3)/2+6”, i.e. 15 microphone sub-arrays.

The signal processing apparatus 102 may select “3 microphonesub-arrays”, i.e. the first microphone sub-array 304A, the secondmicrophone sub-array 304B, and the third microphone sub-array 304C fromthe possible configurations of 15 microphone sub-arrays. The selectionof “3 microphone” sub-arrays in the hexagon arrangement is advantageousas the selected “3 microphone sub-arrays” optimally envelope a 360degree view of the communication environment 100. Further, the selectionof the first microphone sub-array 304A, the second microphone sub-array304B, and the third microphone sub-array 304C, may be further based onthe maximum separation between at least two microphones of the of theplurality of microphones of the microphone-array 106. Moreover, theselected “3 microphone sub-arrays” individually bisect the hexagonalarrangement associated with the microphone-array 106.

With reference to FIG. 3B, there is shown the signal source 104 and thesignal processing apparatus 102 communicatively coupled to themicrophone-array 106. The signal source 104 may be assumed to be locatedat a specific angle (θ) from a reference axis (as shown) of the firstmicrophone sub-array 304A, (60°+θ) with respect to a reference axis (asshown) of the second microphone sub-array 304B, and (120°+θ) withrespect to a reference axis (as shown) of the third microphone sub-array304C.

The signal processing apparatus 102 may be configured to compute therelative time-delay for each of the selected “3 microphone sub-arrays”.The relative time-delay for the first microphone sub-array 304A is amaximum of all the computed relative time-delays. Instead of computingtime-delays for all the 15 microphone sub-arrays, the signal processingapparatus 102 identifies the proximal microphone sub-array with respectto the signal source 104 from computed 3 time-delays.

In some embodiments, the signal processing apparatus 102 maycross-correlate the acoustic signals at the microphone 302A and themicrophone 302D of the first microphone sub-array 304A. Similarly, thesignal processing apparatus 102 may cross-correlate the acoustic signalsat the microphones of the second microphone sub-array 304B and the thirdmicrophone sub-array 304C. The cross-correlation may lead to computationof the relative time-delay, which may be compared with a relationship ofequation (6) or equation (7). In other embodiments, the signalprocessing apparatus 102 may compute the relative time-delay for each ofthe selected set of microphone sub-arrays based on a defined digitalsignal processing technique in the time domain or the frequency domain,for example, Phase Transform (PHAT), Maximum Likelihood Estimation(MLE), Adaptive Least Mean Square (LMS) Filter, Average Square DifferentFunction (ASDF), and the like.

For example, table 1 shows a relationship among relative time-delays forthe selected “3 microphone sub-arrays” and specific values oftime-delays for θ=0°, f_(s)=16000 Hz, and r=4 centimeters.

TABLE 1 Relationship between delay values for the selected set ofsub-arrays Delay Relationship Specific Delay Values Sub-Array (Samples)(Samples) 304A T_(304A)  3.76 304B −T_(304A)/2 −1.88 304C  T_(304A)/21.88From Table 1, it is evident that the first microphone sub-array 304A hasthe maximum delay for aforementioned conditions, and therefore, thefirst microphone sub-array 304A is selected as the desired microphonesub-array. It is advantageous to calculate 3 time-delays instead of 15time-delays as computational complexity is reduced as compared toconventional techniques, such as Multiple Signal Classification (MUSIC),Steered Response Power-Phase Transform (SRP-PHAT) and GeneralizedCross-Correlation (GCC).

In some embodiments, the desired microphone sub-array 304A (alsoreferred to as the first microphone sub-array 304A) may be furtherdetermined from the selected set of microphone sub-arrays when theangular separation between the signal source 104 and the selectedmicrophone sub-array is in a defined range. The defined range of theangular separation may be measured with respect to a specific microphonesub-array, such as the first microphone sub-array 304A. For example, Ifthe reference axis of the first microphone sub-array 304A represents 0°line and the angle increases along clockwise direction, then the firstmicrophone sub-array 304A is the determined first microphone sub-arraywhen the DOA (θ) of the acoustic signals is in a range of −30° to 30°degrees for the microphone 302A and 150° to 210° for the microphone302D. The second microphone sub-array 304B is selected as the determinedfirst microphone sub-array when the DOA (θ) of the acoustic signals isin a range of 30° to 90° degrees for the microphone 302B and 210° to270° for the microphone 302E. The third microphone sub-array 304C isselected as the determined first microphone sub-array when the DOA (θ)of the acoustic signals is in a range of 90° to 150° degrees for themicrophone 302C and 270° to 330° for the microphone 302F.

Based on the relationship of equation (6) or equation (7) and thecomputed relative time-delay from equation (3) or equation (5), the DOAmay be estimated. For example, for f_(s)=16 kHz, r=0.04 m, v_(s)=340m/s, and T_(D)=3.76 samples, the signal processing apparatus 102 maydetermine the DOA (θ) with respect to the desired microphone sub-array304A using equation (7) as:

$\theta = {{\cos^{- 1}\frac{340 \times 3.76}{2 \times 0.04 \times 16000}} = {{\cos^{- 1}0.99875} = 2.865^{{^\circ}}}}$

FIG. 4 is a flowchart that illustrates exemplary operations forestimation of DOA of signals from an acoustic source using sub-arrayselection, in accordance with various exemplary embodiments of thedisclosure. FIG. 4 is explained in conjunction with FIGS. 1, 2, 3A and3B. In FIG. 4, there is shown a flowchart 400 that comprises exemplaryoperations from 402 through 418. The exemplary operations for the DOAestimation of the acoustic signals may start at 402 and proceed to 404.

At 404, a plurality of microphone sub-arrays may be identified from aplurality of microphones in the microphone-array 106. The array selector210 may be configured to identify the plurality of microphone sub-arraysfrom the plurality of microphones in the microphone-array 106.

At 406, a distance between each pair of microphones of the identifiedplurality of microphone sub-arrays of the microphone-array 106 may bedetermined with reference to the microphone-array 106. The arrayselector 210, in conjunction with the processor 206, may be configuredto determine the specific distance between each pair of microphones ofthe identified plurality of microphone sub-arrays of themicrophone-array 106.

At 408, set of microphone sub-arrays may be selected from themicrophone-array 106 based on a determined maximum distance between eachpair of microphones of the identified plurality of microphone sub-arraysof the microphone-array 106. The array selector 210 may be configured toselect a set of microphone sub-arrays from the microphone-array 106based on the determined maximum distance between each pair ofmicrophones of the identified plurality of microphone sub-arrays of themicrophone-array 106. Such selection of the set of microphone sub-arraysmay be referred to as sub-array decomposition of the microphone-array106.

At 410, a relative time-delay may be computed for arrival of theacoustic signals between each pair of microphones of the selected set ofmicrophone sub-arrays. The DOA estimator 212, in conjunction with theprocessor 206, may be configured to compute the relative time-delay forarrival of the acoustic signals between each pair of microphones of theselected set of microphone sub-arrays. Such computation of the relativetime-delay may be based on the cross-correlation of the acoustic signalsreceived at two different microphones of the set of microphonesub-arrays.

At 412, a first microphone sub-array may be determined from the selectedset of microphone sub-arrays based on a maximum time-delay from computedrelative time-delay for each selected set of microphone sub-arrays. Thedetermined first microphone sub-array may be a desired microphonesub-array from the identified plurality of microphone sub-arrays in themicrophone-array 106. The DOA estimator 212 may be configured todetermine the determined first microphone sub-array from the selectedset of microphone sub-arrays. The determination may be based on themaximum time-delay from computed relative time-delay for each selectedset of microphone sub-arrays.

At 414, a DOA of the acoustic signals may be estimated with reference tothe determined first microphone sub-array based on the computed relativetime-delay for the acoustic signals at two different microphones of thedetermined first microphone sub-array (or the desired microphonesub-array). The DOA estimator 212 may be configured to estimate the DOAof the acoustic signals with reference to the determined firstmicrophone sub-array based on the computed relative time-delay for theacoustic signals at two different microphones of the determined firstmicrophone sub-array (or the desired microphone sub-array). Controlpassed to end at 416.

While the present disclosure has been described with reference toillustrative embodiments, this description is not intended to beconstrued in a limiting sense. Various modifications and combinations ofthe illustrative embodiments, as well as other embodiments of theinvention, will be apparent to persons skilled in the art upon referenceto the description. For example, various embodiments described above maybe combined with each other.

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and/or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing first one or more lines of code and maycomprise a second “circuit” when executing second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. As another example,“x, y, and/or z” means any element of the seven-element set {(x), (y),(z), (x, y), (x, z), (y, z), (x, y, z)}. As utilized herein, the term“exemplary” means serving as a non-limiting example, instance, orillustration. As utilized herein, the terms “e.g. and for example” setoff lists of one or more non-limiting examples, instances, orillustrations. As utilized herein, circuitry is “operable” to perform afunction whenever the circuitry comprises the necessary hardware andcode (if any is necessary) to perform the function, regardless ofwhether performance of the function is disabled, or not enabled, by someuser-configurable setting.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of embodiments ofthe disclosure. As used herein, the singular forms “a”, “an” and “the”are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It will be further understood that theterms “comprises”, “comprising,”, “includes” and/or “including”, whenused herein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Further, many embodiments are described in terms of sequences of actionsto be performed by, for example, elements of a computing device. It willbe recognized that various actions described herein can be performed byspecific circuits (e.g., application specific integrated circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. Additionally, these sequence ofactions described herein can be considered to be embodied entirelywithin any non-transitory form of computer readable storage mediumhaving stored therein a corresponding set of computer instructions thatupon execution would cause an associated processor to perform thefunctionality described herein. Thus, the various aspects of thedisclosure may be embodied in a number of different forms, all of whichhave been contemplated to be within the scope of the claimed subjectmatter. In addition, for each of the embodiments described herein, thecorresponding form of any such embodiments may be described herein as,for example, “logic configured to” perform the described action.

The present disclosure may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

Further, those of skill in the art will appreciate that the variousillustrative logical blocks, modules, circuits, algorithm, and/or stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, firmware, orcombinations thereof. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

The methods, sequences, and/or algorithms described in connection withthe embodiments disclosed herein may be embodied directly in firmware,hardware, in a software module executed by a processor, or in acombination thereof. A software module may reside in RAM memory, flashmemory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, aremovable disk, a CD-ROM, or any other form of storage medium known inthe art. An exemplary storage medium is coupled to the processor suchthat the processor can read information from, and write information to,the storage medium. In the alternative, the storage medium may beintegral to the processor.

While the present disclosure has been described with reference tocertain embodiments, it will be noted understood by, for example, thoseskilled in the art that various changes and modification could be madeand equivalents may be substituted without departing from the scope ofthe present disclosure as defined, for example, in the appended claims.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the present disclosure withoutdeparting from its scope. The functions, steps, and/or actions of themethod claims in accordance with the embodiments of the disclosuredescribed herein need not be performed in any particular order.Furthermore, although elements of the disclosure may be described orclaimed in the singular, the plural is contemplated unless limitation tothe singular is explicitly stated. Therefore, it is intended that thepresent disclosure not be limited to the particular embodimentdisclosed, but that the present disclosure will include all embodimentsfalling within the scope of the appended claims.

What is claimed is:
 1. A system for processing acoustic signals,comprising: a microphone-array comprising a plurality of microphones;and a signal processing apparatus comprising a plurality of circuitsassociated with the microphone-array, wherein the plurality of circuitsis configured to: identify a plurality of microphone sub-arrays from theplurality of microphones in the microphone-array, wherein eachmicrophone sub-array of the identified plurality of microphonesub-arrays comprises a pair of microphones spaced apart by a specificdistance; select a set of microphone sub-arrays from the identifiedplurality of microphone sub-arrays of the microphone-array based on amaximum distance between each pair of microphones of the plurality ofmicrophone sub-arrays of the microphone-array; compute a relativetime-delay for an arrival of the acoustic signals between each pair ofmicrophones of the selected set of microphone sub-arrays, wherein therelative time-delay corresponds to an estimated time-delay for thearrival of the acoustic signals between each pair of microphones of theselected set of microphone sub-arrays; determine a first microphonesub-array from the selected set of microphone sub-arrays based on amaximum time-delay from the computed relative time-delay for each of theselected set of microphone sub-arrays, wherein the determined firstmicrophone sub-array is a desired microphone sub-array from theidentified plurality of microphone sub-arrays in the microphone-array;and estimate a direction of arrival of the acoustic signals withreference to the determined first microphone sub-array, based on thecomputed relative time-delay for the arrival of the acoustic signals atthe determined first microphone sub-array.
 2. The system according toclaim 1, wherein the direction of arrival of the acoustic signals withreference to the determined first microphone sub-array is estimatedbased on one or more parameters, and wherein the one or more parameterscomprises a sampling frequency of the acoustic signals, a speed of theacoustic signals, the computed relative time-delay for the determinedfirst microphone sub-array, and a radius associated with a planararrangement of the microphone-array.
 3. The system according to claim 1,wherein the direction of arrival of the acoustic signals is estimated inone of a frequency domain and a time domain.
 4. The system according toclaim 1, wherein the direction of arrival of the acoustic signals withreference to the determined first microphone sub-array is estimatedbased on a digital filter that processes the acoustic signals receivedat a first microphone and a second microphone of the determined firstmicrophone sub-array.
 5. The system according to claim 4, wherein thedigital filter for the estimation of the direction of arrival of theacoustic signals is one of an infinite impulse response (IIR) filter ora finite impulse response (FIR) filter that processes the acousticsignals based on one of a cross-correlation, a Fast Fourier Transform(FFT), a Discrete Fourier Transform (DFT) of the acoustic signalsreceived at the first microphone and the second microphone of thedetermined first microphone sub-array.
 6. The system according to claim1, wherein the plurality of circuits is further configured to determinethe specific distance between the pair of microphones of the pluralityof microphone sub-arrays of the microphone-array.
 7. The systemaccording to claim 1, wherein the plurality of microphones are arrangedin the microphone-array in a regular convex polygon arrangement, andwherein each microphone in the microphone-array is arranged at verticesof the regular convex polygon.
 8. The system according to claim 1,wherein the selection of the set of microphone sub-arrays from themicrophone-array is further based on a planar arrangement of the set ofmicrophone sub-arrays that bisect each other in the microphone-array. 9.The system according to claim 1, wherein the first microphone sub-arrayis determined from the selected set of microphone sub-arrays based on amaximum of the computed relative time-delay among the selected set ofmicrophone sub-arrays.
 10. The system according to claim 1, wherein therelative time-delay for the selected set of microphone sub-arrays iscomputed based on a cross-correlation of the acoustic signals receivedat two different microphones of the selected set of microphonesub-arrays.
 11. The system according to claim 1, wherein the relativetime-delay is computed for each selected microphone sub-array instead ofcomputation of the relative time-delay for each microphone sub-array inthe microphone-array.
 12. The system according to claim 1, wherein thedirection of arrival of the acoustic signals is same as a direction thatcorresponds to a location of a signal source of the acoustic signals.13. A method for processing acoustic signals, comprising: in a signalprocessing apparatus that comprises a plurality of circuits that arecommunicatively coupled to a microphone-array: identifying, by theplurality of circuits, a plurality of microphone sub-arrays from theplurality of microphones in the microphone-array, wherein eachmicrophone sub-array of the identified plurality of microphonesub-arrays comprises a pair of microphones spaced apart by a specificdistance; selecting, by the plurality of circuits, a set of microphonesub-arrays from the identified plurality of microphone sub-arrays of themicrophone-array based on a maximum distance between each pair ofmicrophones of the plurality of microphone sub-arrays of themicrophone-array; computing, by the plurality of circuits, a relativetime-delay for an arrival of the acoustic signals between each pair ofmicrophones of the selected set of microphone sub-arrays, wherein therelative time-delay corresponds to an estimated time-delay for thearrival of the acoustic signals between each pair of microphones of theselected set of microphone sub-arrays; determining, by the plurality ofcircuits, a first microphone sub-array from the selected set ofmicrophone sub-arrays based on a maximum time-delay from the computedrelative time-delay for each of the selected set of microphonesub-arrays, wherein the determined first microphone sub-array is adesired microphone sub-array from the identified plurality of microphonesub-arrays in the microphone-array; and estimating, by the plurality ofcircuits, a direction of arrival of the acoustic signals with referenceto the determined first microphone sub-array, based on the computedrelative time-delay for the arrival of the acoustic signals at thedetermined first microphone sub-array.
 14. The method according to claim13, wherein the direction of arrival of the acoustic signals withreference to the determined first microphone sub-array is estimatedbased on one or more parameters, and wherein the one or more parameterscomprises a sampling frequency of the acoustic signals, a speed of theacoustic signals, the computed relative time-delay for the determinedfirst microphone sub-array, and a radius associated with a planararrangement of the microphone-array.
 15. The method according to claim13, wherein the direction of arrival of the acoustic signals isestimated in one of a frequency domain and a time domain.
 16. The methodaccording to claim 13, further comprising determining, by the pluralityof circuits, the specific distance between the pair of microphones ofthe plurality of microphone sub-arrays of the microphone-array.
 17. Themethod according to claim 13, wherein the plurality of microphones arearranged in the microphone-array in a regular convex polygonarrangement, and wherein each microphone in the microphone-array isarranged at vertices of the regular convex polygon.
 18. The methodaccording to claim 13, wherein the selection of the set of microphonesub-arrays from the microphone-array is further based on a planararrangement of the set of microphone sub-arrays that bisect each otherin the microphone-array.
 19. The method according to claim 13, whereinthe first microphone sub-array is determined from the selected set ofmicrophone sub-arrays based on a maximum of the computed relativetime-delay among the selected set of microphone sub-arrays.
 20. Themethod according to claim 13, wherein the relative time-delay for theselected set of microphone sub-arrays is computed based on across-correlation of the acoustic signals received at two differentmicrophones of the selected set of microphone sub-arrays.